Property Value

Type: String
Contains the sender's mail server domain name and/or IP address as specified in the Received header, or an empty string
if from field is missing in the Received header.

Remarks

Typical examples of this property value: mail.domain.com ([1.2.3.4]),
MYSERVER (mail.domain.com [1.2.3.4]), etc. There is no strict format for this value.

This value does not necessarily denote the original host which sent this message. Instead, it contains the name
of the host which delivered the message to the host which added this time stamp to the message. If the delivery chain
consists of many servers, From server simply denotes the previous link in the chain.